src/Tizen.NUI.Components/Controls/RecyclerView/LinearLayoutManager.cs

   1 /* Copyright (c) 2020 Samsung Electronics Co., Ltd.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at
   6  *
   7  * http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  *
  15  */
  16 using System;
  17 using Tizen.NUI.BaseComponents;
  18 using System.Collections.Generic;
  19 using System.ComponentModel;
  20
  21 namespace Tizen.NUI.Components
  22 {
  23     /// <summary>
  24     /// [Draft] This class implements a linear box layout.
  25     /// </summary>
  26     /// <since_tizen> 8 </since_tizen>
  27     /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
  28     [EditorBrowsable(EditorBrowsableState.Never)]
  29     public class LinearListLayoutManager : LayoutManager
  30     {
  31         private int firstVisibleItemIndex = -1;
  32         private int lastVisibleItemIndex = -1;
  33
  34         private bool IsItemVisible(float scrollPosition, RecycleItem item)
  35         {
  36             bool result = false;
  37             View list = Container.GetParent() as View;
  38
  39             Vector2 visibleArea = new Vector2( Math.Abs(scrollPosition),
  40                 Math.Abs(scrollPosition) + (LayoutOrientation == Orientation.Horizontal?
  41                                                 list.Size.Width:list.Size.Height)
  42             );
  43
  44             float firstCheckPoint = LayoutOrientation == Orientation.Horizontal? item.Position.X:item.Position.Y;
  45             float secondCheckPoint = LayoutOrientation == Orientation.Horizontal?
  46                                         firstCheckPoint + item.Size.Width:
  47                                         firstCheckPoint + item.Size.Height;
  48
  49             // Tizen.Log.Error("NUI", "[1p] "+visibleArea.X+ " =< "+firstCheckPoint+" =< "+visibleArea.Y+" ==== \n");
  50             // Tizen.Log.Error("NUI", "[2p] "+visibleArea.X+ " =< "+secondCheckPoint+" =< "+visibleArea.Y+" ==== \n");
  51
  52             result = (firstCheckPoint >= visibleArea.X && firstCheckPoint <= visibleArea.Y) || (secondCheckPoint >= visibleArea.X && secondCheckPoint <= visibleArea.Y);
  53
  54             return result;
  55         }
  56
  57         /// <summary>
  58         /// This is called to find out where items are lain out according to current scroll position.
  59         /// </summary>
  60         /// <param name="scrollPosition">Scroll position which is calculated by ScrollableBase</param>
  61         /// <since_tizen> 8 </since_tizen>
  62         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
  63         public override void Layout(float scrollPosition)
  64         {
  65             firstVisibleItemIndex = -1;
  66             lastVisibleItemIndex = -1;
  67
  68             RecycleItem previousItem = null;
  69
  70             for(int i = 0 ; i < Container.Children.Count ; i++)
  71             {
  72                 RecycleItem item = Container.Children[i] as RecycleItem;
  73
  74                 if(previousItem != null)
  75                 {
  76                     item.Position = LayoutOrientation == Orientation.Horizontal?
  77                         new Position(
  78                             previousItem.Position.X + (previousItem.CurrentSize.Width != 0 ?
  79                                                             previousItem.CurrentSize.Width:
  80                                                             previousItem.Size.Width),
  81                             item.PositionY
  82                         ):
  83                         new Position(
  84                             item.PositionX,
  85                             previousItem.Position.Y + (previousItem.CurrentSize.Height != 0 ?
  86                                                             previousItem.CurrentSize.Height:
  87                                                             previousItem.Size.Height)
  88                         );
  89                 }
  90
  91                 bool isVisible = IsItemVisible(scrollPosition, item);
  92
  93                 if(isVisible)
  94                 {
  95                     firstVisibleItemIndex = firstVisibleItemIndex == -1? i : firstVisibleItemIndex;
  96                     lastVisibleItemIndex = i;
  97                 }
  98
  99                 previousItem = item;
 100
 101                 // Tizen.Log.Error("NUI","["+item.DataIndex+"] "+item.Position.Y+" ==== \n");
 102             }
 103
 104             if(mStepSize == 0)
 105             {
 106                 mStepSize = LayoutOrientation == Orientation.Horizontal?ItemSize.Width:ItemSize.Height;
 107             }
 108         }
 109
 110         /// <summary>
 111         /// This is called to find out which items should be recycled according to current scroll position.
 112         /// </summary>
 113         /// <param name="scrollPosition">Scroll position which is calculated by ScrollableBase</param>
 114         /// <returns>List of RecycleItems which should be recycled.</returns>
 115         /// <since_tizen> 8 </since_tizen>
 116         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 117         public override List<RecycleItem> Recycle(float scrollPosition)
 118         {
 119             List<RecycleItem> result = new List<RecycleItem>();
 120
 121             bool checkFront = (mPrevScrollPosition - scrollPosition) > 0;
 122
 123             if(checkFront)
 124             {
 125                 if(firstVisibleItemIndex > 3)
 126                 {
 127                     // Too many item is in front!!! move first item to back!!!!
 128                     RecycleItem target = Container.Children[0] as RecycleItem;
 129                     target.DataIndex = target.DataIndex + Container.Children.Count;
 130                     target.SiblingOrder = Container.Children.Count - 1;
 131
 132                     result.Add(target);
 133                 }
 134             }
 135             else
 136             {
 137                 if(lastVisibleItemIndex < Container.Children.Count - 3)
 138                 {
 139                     RecycleItem prevFirstItem = Container.Children[0] as RecycleItem;
 140
 141                     RecycleItem target = Container.Children[Container.Children.Count - 1] as RecycleItem;
 142                     target.Position = new Position(
 143                         LayoutOrientation == Orientation.Horizontal ? (prevFirstItem.Position.X - target.Size.Width) : prevFirstItem.Position.X,
 144                         LayoutOrientation == Orientation.Horizontal ? prevFirstItem.Position.Y : (prevFirstItem.Position.Y - target.Size.Height)
 145                     );
 146                     target.DataIndex = target.DataIndex - Container.Children.Count;
 147                     target.SiblingOrder = 0;
 148
 149                     result.Add(target);
 150                 }
 151             }
 152
 153             mPrevScrollPosition = scrollPosition;
 154
 155             return result;
 156         }
 157
 158         /// <summary>
 159         /// Adjust scrolling position by own scrolling rules.
 160         /// </summary>
 161         /// <param name="scrollPosition">Scroll position which is calculated by ScrollableBase</param>
 162         /// <since_tizen> 8 </since_tizen>
 163         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 164         public override float CalculateCandidateScrollPosition(float scrollPosition)
 165         {
 166             return scrollPosition;
 167         }
 168     }
 169 }